The Spirit Bucket is a bucket that contains liquid spirit from the Witchery mod. This liquid is only obtainable by traveling to the Spirit World. Throwing Brews of Flowing Spirits at the ground will spawn the Flowing Spirit, which can be picked up with a bucket. Standing in this liquid will grant the creature the Regeneration effect. If a Nightmare stands in the liquid, it will lose its invulnerability power.
Flowing Spirit source blocks will reduce the player's chance of experiencing a nightmare when entering the Spirit World by 10% each. Up to three source blocks within an 8 block radius of the player will have this effect.
As of Witchery version 0.17.0, the Flowing Spirit liquid is not available as a Mystcraft page.